A Diploma Thesis titled ‘Investigation of the impact on road safety of increasing the speed limit on motorways‘ was presented by Eleni Georgiadou in January 2014. The objective of this Diploma Thesis is to investigate the impact on road safety of increasing the speed limit on motorways from 120 to 130 km/h in June 2007. In order to achieve this objective, data was collected concerning road accidents on motorway sections Athens – Thebes and Athens – Tripoli from the database of Department of Transportation Planning and Engineering of the N.T.U.A. with data from the Hellenic Statistical Authority and on sections of the Egnatia Motorway from Egnatia Odos S.A. for the period 2005 – 2010. The application of the methodology indicates a statistically significant increase in the number of deaths in the section Athens – Thebes a year after raising the speed limit, possibly due to the increase of the speed limit, and then ceases to be statistically significant, probably due to improvements made to the infrastructure. In the section Athens – Tripoli a reduction in accidents and victims is indicated probably due to improvements in the infrastructure while in the Egnatia Motorway there is no statistically significant change possibly due to the high geometrical characteristics of the road which might satisfy the higher speed limit.